You are not alone. I also see I also see "error DLNA protocol 7531". For that reason I have never had success with PS3MS--it shows up on my PS3 with the wrong icon and the PS3 shows up in PS3MS. But no files appear on the PS3, so nothing can be played. Only the DLNA error when I click on the icon. I have tried many builds and just about everything else i can think of, with no solution. Other media servers work without this error.

After countless hours of nosing around, I found my problem. I hope this works for anyone else who has a similar configuration.

The culprit in my case was NETLIMITER. Disabling the Netlimiter service in Vista (control panel>administrative tools>services) allowed PS3MS to work like a charm.

I started getting suspicous when I installed Jamcast to use as a media server for my Roku Soundbridge devices and it recognized the devices but they wouldn't see the media server. I figured if two media servers weren't working properly (although all others seemed to work fine) then I must be missing something. And the something I was missing, apparently, was Netlimiter.